Recently, the use of a wearable device is increasing. In this case, the wearable device may correspond to devices including a smart watch, a HMD, and the like. In particular, the wearable device may correspond to a device worn on a user. In this case, the wearable device may have a limitative display area. Hence, it is necessary to have a method of using the wearable device by extending the display area of the wearable device.